1. Field of the Disclosure
The present disclosure is directed to apparatuses and methods for the combustion of a carbonaceous fuel with oxygen at high pressure and high temperature to produce combustion products which are either oxidized with an excess of oxygen, or which contain reducing components and have zero oxygen content. One particular application would be for generation of energy, such as electricity, through the use of a working fluid to transfer energy generated through high efficiency combustion of a fuel. Particularly, such apparatuses and methods can use carbon dioxide or steam as the working fluid. In another aspect, the apparatuses and methods may be used to generate a gas containing hydrogen and/or carbon monoxide.
2. Description of Related Art
It is estimated that fossil fuels will continue to provide the bulk of the world's electric power requirements for the next 100 years, while non-carbon power sources are developed and deployed. Known methods of power generation through combustion of fossil fuels and/or suitable biomass, however, are plagued by rising energy costs and an increasing production of carbon dioxide (CO2) and other emissions. Global warming is increasingly seen as a potentially catastrophic consequence of increased carbon emissions by the developed and developing nations. Solar and wind power do not appear capable of replacing fossil fuel combustion in the near term, and nuclear power has dangers associated with both proliferation and nuclear waste disposal.
Conventional arrangements for power production from fossil fuels or suitable biomass are now being increasingly burdened with a requirement for CO2 capture at high pressure for delivery to sequestration sites. This requirement is proving difficult to fulfill, however, since present technology only provides for very low thermal efficiencies for even the best designs for CO2 capture. Moreover, capital costs for achieving CO2 capture are high, and may thus result in significantly higher electricity costs compared to systems that emit CO2 into the atmosphere. Accordingly, there is an ever growing need in the art for apparatuses and methods for high efficiency power generation with a reduction in CO2 emission and/or improved ease of capture and sequestration of produced CO2.
Oxy-fuel combustion of carbonaceous fuels involves the separation of substantially pure oxygen from air (or otherwise providing such substantially pure oxygen for use in the combustion process) and using the oxygen as a combustion medium to produce combustion products which are substantially free of nitrogen and which comprise carbon dioxide and water vapor. Current art air and oxy-fuel combustors operate at limited temperatures and pressures to prevent excess-temperature damage to the combustor walls and/or to other system components, such as turbine blades. Limiting the operating temperature and/or pressure may, in some instances, undesirably lengthen the combustion process and/or require a relatively large combustion volume. In addition, the combustion process, the combustion design, and/or the downstream exhaust gas processing provisions may also be undesirably dependent on the type of fuel utilized for the process. Further, due to the large volumes of combustion gases applied to conventional boiler systems in the current art, and the exhaust of these gases to atmosphere, current methods of removing pollutants from exhaust smokestack gases and proposed oxy-fuel combustion systems are highly dependent on the detailed design of the plant and on the exact type of fuel burned in the plant. Each type of fuel has a contrasting chemical composition and amount of pollutants. Thus, current art undesirably requires that the exhaust gas scrubber systems or oxy-fuel combustion modifications for each plant be custom-designed specifically to accommodate a particular type of fuel with a particular chemical composition.
The current art for coal, as an example, generally utilizes a very large single combustor equipped with vertical tubular walls or helically-configured tubular walls in which steam at high pressure is generated and superheated in a separate superheater section. The large-size combustor may experience significant heat loss, and in general is subject to damage, as well as fouling of the burners, radiant and convective heat transfer surfaces and other components, from coal ash, slag and corrosive components, such as SOX, HCl, NOX, etc., in the combustion gases depending on the particular coal used. Such exemplary shortcomings may require that the entire plant be shut down to repair or replace damaged or corroded parts and/or other components at periodic intervals, and may thus result in lower availability of the plant and undesirable difficulties in compensating for the lost output of the plant during down times.